1. Field of the Invention
The present invention relates to a solid electrolytic capacitor and a method of manufacturing the same.
2. Description of Related Art
In general, a solid electrolytic capacitor is formed in the following manner. Firstly, an anode made of a valve metal such as niobium (Nb) and tantalum (Ta) is anodized, so that a dielectric layer chiefly made of an oxide is formed on the surface of the anode. Subsequently, an electrolytic layer is formed on this dielectric layer, and lastly, a cathode layer is formed on the electrolytic layer. For example, Japanese Patent Application Laid-Open Publication No. Hei. 4-48710 discloses the structure of the electrolytic layer, which is formed by laminating a second electrically-conductive polymer layer made of polypyrrole formed through electrolytic polymerization to a first electrically-conductive polymer layer made of polypyrrole formed through chemical polymerization.
However, this type of solid electrolytic capacitor has a problem that the dielectric layer and the electrolytic layer delaminate in the interface between the two layers, and that the delamination decreases the electrostatic capacitance of the solid electrolytic capacitor. When the solid electrolytic capacitor is thermally treated particularly in a high-temperature test and in a reflow step carried out when parts are packaged on a board, the delamination in the interface is more serious. This delamination further decreases (deteriorates) the electrostatic capacitance of the solid electrolytic capacitor. For this reason, it has been recently strongly urged that these types of characteristics of the solid electrolytic capacitor should be improved.